(a) Field of the Invention
The present invention involves a kind of prepolymer, and from which producing a kind of high-performance thermosetting resin composition corresponding to the packaging requirements for electronic components and Integrated Circuits (IC).
(b) Description of the Prior Art
Increasing demands on light-weight, small-scale and high densification for electronic and communication products are driving the development of printed circuit board towards thinning and microporosity techniques. In addition to continued improvement with miniaturization of Surface Mounting Technology (SMT), the demand on high quality IC package substrate is boosted constantly.
For conventional IC package, the wire frame is used as the IC conducting circuit and the vehicle for IC, connected to the pins on sides or circumference. With the development of IC package technology, the increase of the number of pins (over 300 pins), the routing density augment, and the increase of the number of layers of substrates, limit its development for the traditional package method such as QFP (Quad Flat Package) etc. In the mid 90s of 20th century a new type of IC package method represented by BGA (Ball Grid Array Package), CSP (Clip Scale Package) comes out, along with yielding a new necessary carrier for semiconductor chip package, i.e. IC package substrate (also named IC package carrier).
For the past years, IC package substrate as BGA, CSP and FC (Flip Chip) modes is expanded rapidly and widely in its application field. In the world, the strong competitive situation is going on in the market of package substrate in the countries and regions to deal with the package manufacturing. The competition is with focus on fully applying high density multilayer substrate technique to IC package and reducing the cost of manufacturing package substrate.
To develop the substrate material used for IC package carrier (also named IC package substrate) is very important task currently. Along with the development of IC package towards high frequency, low electric energy consumption, the major performance of IC package substrate such as low dielectric constant, low dielectric loss factor, high thermo-conductivity will be improved. An important direction for studying IC package carrier is effectual heat coordination and integration such as heat connection techniques and heat dispersal of substrate etc. The great amount of heat generated with power consumption by electronic components would lead to increase the temperature of device. In general, the probability of invalidation for a device increases 2˜3 times with each 18° C. temperature rise. Therefore it is particularly important to solve the problem about heat dissipation by improvement of the heat conducting performance of package material, to assure normal operation of the circuit within the operating temperature range.
The other problem to be solved is that the coefficient of thermal expansion for IC package carrier is incongruent with it of semiconductor chips. Even if the build-up multi-layer boards suited for minuteness circuit manufacturing technology, the problem about common excessive thermal expansion coefficient of insulated substrate (typically the thermal expansion is about 60 ppm/° C.) also exists. To make the coefficient of thermal expansion of substrate reach 6 ppm or so near that of semiconductor chips is surely a “formidable challenge”.
The development of IC package design and manufacturing technique puts forward the more strict requirements with substrate materials used for it. These are shown mainly in the following aspects: 1) high Tg and high thermotolerance corresponding the lead-free fluxes; 2) the property of low dielectric loss factor requiring to reduce the signal transmission loss; 3) low dielectric constants for speedup; 4) low warpage (improvement of the flatness of substrate surface); 5) low hydroscopicity; 6) low coefficient of heat expansion, making it close to 6 ppm; 7) low cost of the IC package substrates; 8) low cost of the built components; 9) high strength characteristics at high temperature; 10) the environmentally friendly substrate material to lower the cost suited for lead-free reflow soldering process.
The most of substrate used for IC package is made up of organic resins. Many resins as epoxide resin, acrylate resin, cyanate resin and bismaleimide-triazine (BT) resin have been used in this field.
Epoxide resin is the most common resin to be used; it has easy processing, good cohesive property with all substrates, high chemical resistance and corrosion resistance, excellent mechanical property etc. But the performance of epoxide resin at high temperature is not good enough, mainly higher dielectric constant (for example, the epoxide resin-basic package carrier E-679F developed by Hitachi Chemical Co., Ltd. has dielectric constant of 4.85 and 4.53 corresponding at frequency 1 MHz and 1 GHz respectively) and greater water absorption rate. Epoxide resin is cured with amides and anhydrides normally, so that the cured material inevitably contains considerable amount of hydrophilic groups as hydroxyl group, leading to greater water absorption rate of the material. Therefore, the cured epoxide resin is very sensitive to water at high temperature and high humidity.
The performance of cyanate resin has reasonable improvement compared to conventional epoxide resin. Cyanate resin is required usually in order to get high cross-linking density, high glass transition temperature (Tg) and lower dielectric nature. However, cyanate resin has itself high cost and weaknesses such as high brittleness, high water absorbtivity after it cured.
Another primary resin is bismaleimide. Its characteristic is that the physical property remained considerable excellent at high temperature and high humidity, and steady electric property within wide range of temperature (no fluctuations). This characteristic makes bismaleimide ideal for use in the field of advanced complex material and electronics, electrical appliances. Bismaleimide has good damp and hot performance at high temperature of 230-250° C. But bismaleimide is insoluble in conventional organic solvents normally, so difficult for processing. Further more, the weaknesses for bismaleimide that the curing condition too severe and too great brittleness which makes easy produce micro-cracks under thermal shock also exist.
Popularly, bismaleimide is used in combination with cyanate, to get the usually so-called BT resin. This kind of resin was developed and patented by Mitsubishi Gas Co., Ltd. Japan at the earliest (U.S. Pat. No. 4,110,364).
Bismaleimide-triazine resin (BT resin, for short) is a high polymer resin resulted from copolymerization of cyanate resin with —OCN (CE) and bismaleimide resin (BMI) at 170-240° C. The finalized high polymer is composed of N-heterocyclic structure with high heat resistance as triazine ring, imide ring etc. The solids of such BMI/CE copolymer have impact resistance, electricity insulativity (shown mainly at low ∈, low tan δ) and process operationables as BMI resin, as well as improved water resistance of cyanate resin simultaneously, and maintain high heat resistance possessed by the both.
Since the substrate material made from BT resin is the best in PCT (Pressure Cooker Test) resistance, metallic ion migration resistance, heat resistance, dielectric property, humidity resistance and elevated temperature impact property, specially its mechanic properties at high temperature (including mainly flexural strength, elastic modulus, copper foil adhesive strength and surface hardness etc. at high temperature) have more outstanding advantage compared with the substrate materials made from other resins (such as the substrate materials made from common epoxide resin, polyimide resin, polyphenyl ether resin), therefore the insulation reliability and technical processability for chip setting and high density wire laying on IC substrate package application are improved, thus the substrate material made of BT resin makes up a major part of all kinds of substrate material.
But due to the crosslinking density of BT resin after polymerization large, plus the triazine ring structure in molecule high symmetreal, crystallinity high, that bring about the solids more brittle, and the price expensive resulting from complicated syntheses process of cyanate resin (CE) used, therefore increasing ductility and processability and reducing the cost is where the work centre of many derived patents is since the BT resin patent published by Mitsubishi Gas Co., Ltd. on August, 1978. The patents on this area are so vast: U.S. Pat. Nos. 4,456,712, 4,683,276, 4,749,760, 4,847,154, 4,902,778, 4,927,932, 4,996,267, 6,534,179, 6,774,160, JP1197559, JP7070316, JP200129468, JP2006169317, JP2006022309 etc., too numerous to enumerate.
Further more, the epoxide resin/bismaleimide system, BT resin etc. are unable to form a stable solution in all kinds of low-boiling solvent. For easy to prepreg, it is required usually to use the high boiling-point intensive polarity solvent as dimethyl formamide (DMF) and N-methylpyrrolidone etc. to help dissolution. And application of DMF and N-methylpyrrolidone solvents etc. will speed up the reactivity of resin system and severely affect the gelation time of resin composition, bring some problems along topping with gum.
In the case of using 4-(maleimide phenyl)glycidol ether (MPGE) epoxide resin directly with DICY or phenol formaldehyde resin as curing agent, applied to manufacturing of copper clad panel, the glass transition temperature can only reach about 170° C. In order to increase the glass transition temperature further, it is necessary to take modification to bismaleimide. If just simple blending, the phase separation would be brought since poor consistency between the both, that is not suit prepreg process. Therefore it is required to take a prepolymerization process for it.
Whereas this, the present inventor study it, with aim to develop a prepolymer, which can be applied to manufacturing high performance thermosetting resin composition, and to apply the prepolymer to manufacturing high performance thermosetting resin composition corresponding to the package requirements of electronic components and integrated circuit (IC), to make its price low, and not use high boiling-point polar solvent as DMF and N-methylpyrrolidone etc., but to be able to dissolve in the common low boiling-point non-polar solvents as acetone, toluene, dichloromethane, butanone or methyl isobutyl ketone to form stable solution. Therefore this case is brought.